Conveyor systems in which a substantially endless track is provided at one or more levels with horizontal, inclined or vertical stretches and cars or other vehicles travel along this track and are diverted from the track to various branches or stations have become of increasing importance in recent years and have gained widespread interest in a variety of applications, e.g. for the handling of articles, information and goods and, indeed, wherever an article must be transported from one station to another station along the track.
Typical uses of such installations are in mail-handling facilities in offices and in banks where generally the articles consist of documents, envelopes, packages or papers, or warehouses or factories where the articles may consist of parts to be assembled, inventoried or processed. Other applications of such installations will be readily apparent to the reader.
Existing installations of this type (see U.S. Pat. No. 3,636,883, for example) utilize a track which, for each station at which a car or vehicle can be removed from the track, consists of an arrival-and discharge-track stretch, a transfer station between this stretch and a main-track stretch from which the car can be shifted at this location assuming that a code set on a car matches the code designation for that station as determined by a code reader.
The coding of the car can be established by one or more movable members displaceable in movable guides parallel to the direction of travel and whose positions on the car with respect to a reference marker establish the code. The reference marker and code-setting member or members may be permanent magnets and the code reader at the station may be reed switches or other devices sensitive to the permanent magnets.
The code is usually carried on one side wall of the car and the transfer station between arrival-and discharge-track stretch and main-track stretch can be provided as a detecting station responsive to the position of the code-setting markers with respect to the reference marker.
When the track or siding of the station is filled, however, means responsive to the availability of space on this siding can be provided to prevent the transfer station from operating to feed additional cars thereto and, as a result, the car destined for a particular station is not diverted onto this siding, but rather is permitted to circulate until the siding becomes free again to receive this car.
Naturally, this may result in an undesired circulation of large numbers of cars unnecessarily and repeatedly, placing a significant load upon the system.